Jane/Derek/Adrian - someone add a revised ID for wood mouse Apodemus sylvaticus and then people can agree with that.
BTW could have been yellow-necked mouse in this location too, but I think the second photo shows there's no shoulder-to-shoulder band of darker fur.

The two species are difficult to distinguish, but the easy 'knock-out' question for the yellow-necked mouse is often the location (have a look on the NBN Gateway maps) - wood mice are widely distributed throughout England, Wales & Scotland whereas the yellow-necked has a much more restricted distribution.

The yellow-necked is larger than the wood, but with such a small animal it's often difficult to get a good sense of scale and of course juveniles and 'atypical' individuals can invalidate that comparison anyway.

In terms of colour, the 'brown' on a wood mouse may be more reddish, but the difference isn't that great and again individuals may show colour variations.

So if the animal is sighted somewhere that is within the range of both species, the only definite way to tell is if you get a good view of the neck/chest markings. Yellow-necked mice havea continuous band of brown from shoulder to shoulder (see reluctantly obliging mouse at http://www.ispot.org.uk/node/238018) whereas in wood mice there is only a spot or short vertical stripe of brown, sometimes likened to a clip-on tie.

Which is why, if the chest markings can't be seen from the photo and both species could be present at that location, we tend to just say 'Apodemus species'.
But I think the side view of the mouse in the second photo suggests no band of brown from shoulder to shoulder?

Hi Gill,
Thank you for the description and the link. I’m now pleased to say I almost certainly have seen a yellow-necked mouse and even have a photo somewhere on my camera. I’ll see if I can find and upload it to ispot tomorrow.